I've got an older 65" Mitsubishi and using cable for HD. I recently got an upgraded dual tuner box and now my HD channels are stuttering. It worked fine the first couple of days. At first I just assumed it was the cable and have a tech coming early in the week, but now I'm wondering if it could be the TV? Even recorded HD shows recorded prior to the problem are stuttering. Is there anything in the TV that could go bad and cause this?